1. Field of the Invention
The present invention relates to networking a computer system, and more particularly to a converter that speeds up conversion of signals between a Serial Media Independent Interface (SMII) and a Media Independent Interface (MII) regardless of a reduction in the number of pins that are available.
2. Description of the Related Art
Many computer systems today are utilized in a network configuration where each network computer can transmit data to other computers on the same network. Various systems and related protocols have been developed over the years to implement such networks, such as Ethernet, Token Ring, and ATM. Depending upon which network protocol is utilized, certain requirements must be met, such as the type of hardware used and particular data characteristics.
The Ethernet network is a well-known communication network and is considered by many to be the most popular LAN system in use today. Since the beginning of the Ethernet protocol in the early 1970s, computer networking companies and engineering professionals have continually strove to improve Ethernet product versatility, reliability and transmission speeds. To ensure that new Ethernet products were compatible and reliable, the Institute of Electrical and Electronic Engineers (IEEE) formed a working group to define and promote industry LAN standards. Today, the IEEE has various Ethernet working groups that are responsible for standardizing the development of new Ethernet protocols and products under an internationally well-known LAN standard called the “IEEE 802.3 Standard”.
In general, the Ethernet network provides for communication of computer data amongst user nodes attached to the network. A 10-Base Ethernet system operates to transmit data packets from a source address to a destination address at a speed of 10 Mbps (megabits per second). A faster system is the 100-Base Ethernet system which similarly operates to transmit data packets from a source address to a destination address but at a speed of 100 Mbps. It should be noted, however, that the traditional Ethernet network is a bus type topology. As such, the Ethernet network has been traditionally confined to LAN applications. For example, the 10/100-Base Ethernet bus is typically limited to approximately 100 feet from node to node, such as for use in small buildings and the like.
Efforts to improve the networking of digital computers and the transmission of digital data have been the object of significant research and development in the past. Networking allows computers to share resources, access huge stores of information, communicate via e-mail, share data, and transfer files. Networking technology and digital data transmission have been subject to a number of bandwidth and speed limitations.
In the past, networking technology has suffered from limitations on data transmission rates which limit the bandwidth of the system. For example, local area networks (LANs) may be connected with cables that have finite limitations on the amount of data they can pass, and the speed at which it can be done. LANs may be connected to extended wide area networks (WANs) over transmission lines that have bandwidth limitations. When modems are required for communication over conventional telephone lines, severe limitations may be imposed upon data transmission rates.
Currently, there are a wide variety of standard Ethernet compliant products used for receiving, processing, and transmitting data over Ethernet networks. These products include, by way of example, network interface card (NICs), routers, switching hubs, bridges, and repeaters. Until recently, common data transmission speeds over Ethernet networks were 10 Mbps. However, to meet the demand for faster data transmission speeds, the IEEE 802.3 Standards Committee officially introduced another standard—the IEEE 802.3u Standard—for a 100BASE-T system capable of performing data transmission at up to 100 Mbps. When operating with a UTP cable as a transmission medium, these networks are commonly referred to as 10BASE-T and 100BASE-T networks.
Network devices generally adhere to an open systems interconnection (OSI) layered model developed by the International Organization for Standards (ISO) for describing the exchange of information between layers. The OSI layered model is particularly useful for separating the technological functions of each layer, and thereby facilitating the modification or update of a given layer without detrimentally impacting the functions of neighboring layers.
Multiple layers defined in the OSI model are responsible for various functions, including: providing reliable transmission of data over a network; routing data between nodes in a network; initiating, maintaining, and terminating a communication link between users connected to the nodes; performing data transfers within a particular level of service quality; controlling when users are able to transmit and receive data depending on whether the user is capable of full-duplex or half-duplex transmission; translating, converting, compressing, and decompressing data being transmitted across a medium; and providing users with suitable interfaces for accessing and connecting to a network. The lower portion of the OSI model includes a media access control (MAC) layer, which generally schedules and controls the access of data to a physical layer (PHY).
At the lower most portion of the OSI model, the PHY layer is responsible for encoding and decoding data into signals that are transmitted across a particular medium, such as a cable. To enable transmission to a particular medium, the PHY layer also includes a physical connector which is configured and operable to receive the cable. In addition, the cable can take various forms, including that of an unshielded, twisted pair (UTP) cable, which is used for various types of Ethernet transmission, including 10BASE-T and 100BASE-T.
In order for a network to accommodate a number of users efficiently, routing and flow control procedures have to be established. There are many rules that must be followed, and these rules are typically referred to as protocols. Packet-switched networks subdivide digital data messages into packets. The digital data is then transmitted packet by packet. Each packet must contain not only the information bits comprising the digital data that is to be transmitted, but also information bits which are overhead required by the protocol in use, such as information bits which identify the destination of the packet, the source of the packet, and synchronization bits. Overhead bits typically appear in a header and trailer to each packet. In addition, acknowledgement packets must be transmitted over the network to confirm receipt of a packet of data. Alternatively, a protocol may include information in the overhead bits in each packet indicating the number of the packet. This information may be used to reassemble the received packets in the correct order, and if a packet is missing, a negative acknowledgement packet may be sent to request retransmission of the missing packet. Otherwise, data loss could occur and not be detected by the system. In any event, acknowledgement packets and other similar handshaking information which must be transmitted over the network according to the protocol impose some limitations upon the data throughput of the network. While this may be acceptable in many instances, in applications where the transfer of huge amounts of data are required, these bandwidth limitations may render such applications impractical in practice.
It is not uncommon for two or more users on a network to attempt to transmit a packet at the same time. When this occurs, it is referred to as a collision. Neither packet will be received successfully, and both must be retransmitted. Obviously, this reduces the throughput of the network. Different protocols employ various schemes to determine the timing of retransmission attempts in an effort to avoid repeated collisions between the same two users.
Data transmission may sometimes experience data errors, where a digital “1” is erroneously received as a “0”, or vice versa, due to such events as signal fluctuations or noise. Thus, error correction schemes may be employed in an effort to detect data errors. If an error is detected, then a packet must be retransmitted. Of course, when a packet must be retransmitted, it reduces the overall throughput of the network.
Networking technology has suffered from limitations resulting from a proliferation of non-standard protocols, and limitations due to the nature of the protocols and transmission schemes which are employed. Additional overhead may be imposed when conversion from one protocol to another is required. This additional overhead may effectively limit the overall bandwidth of the network.
Networks may need to be connected by hubs, routers, and other switches. A hub, for example, may have a number of ports, and each port may be connected to a network, such as a LAN or a wide area network. When a packet is received at a hub, the hub switch must determine to which port the packet is to be switched. Alternatively, the packet may be switched to all ports and broadcast over every network connected to the hub. However, if every hub broadcasts every packet on every port, the amount of traffic on the network will be increased and the throughput will invariably suffer. Under heavy traffic, any attempt to determine to which port a packet must be switched must be accomplished speedily to avoid slowing throughput of the network. Therefore, it is desirable to have a method for determining over which port a packet should be transmitted.
In addition to limitations on bandwidth, all of the above discussed factors may affect cost, response time, throughput, delay, maximum transmission rates, and reliability. Many other problems and disadvantages of the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.